The present invention relates to an electrophotographic photoconductor, which can be employed in repetition, and comprises (a) an electroconductive support, (b) an undercoat layer containing therein at least one salt selected from the group consisting of carboxylates, amino carboxylates, phosphates, polyphosphates, phosphites, phosphate derivatives, borates, sulfates and sulfites, and (c) a photoconductive layer, which layers are successively overlaid on the electroconductive support.
Electrophotographic photoconductors are widely employed, for instance, in conventional plain paper copying machine, laser printers and digital copying machines. When an organic photoconductor is employed as such electro-photographic photoconductor, an undercoat layer consisting of a resin having a relatively low electric resistivity is usually interposed between a photoconductive layer and an electroconductive support in order to improve the charge-ability of the photoconductive layer and the adhesion of the photoconductive layer to the support.
As such resins for use in the undercoat layer, for instance, the following resins are proposed: Polyamide resin (Japanese Laid-Open Patent Application Nos. 58-30757 and 58-98739), an alcohol-soluble nylon resin (Japanese Laid-Open Patent Application No. 60-196766), and a water-soluble polyvinyl butyral resin (Japanese Laid-Open Patent No. Application 60-232553).
However, the above resins, when used in the undercoat layer, have the shortcomings that their resistivities increase at low humidities, and the residual potential of the electrophotographic photoconductor increases during the repeated use thereof, so that the image quality obtained is significantly degraded.
In order to prevent the degradation of the image formation characteristics of the electrophotographic photo-conductor while in use, it is proposed to form an undercoat layer comprising a polyamide resin and an electro-conductive polymer in Japanese Laid-Open Patent Application No. 58-95744. This method, however, has the shortcoming that the undercoat layer decreases the photosensitivity of the photoconductor. Further it is proposed to provide an electroconductive pigment in the undercoat layer in Japanese Laid-Open Patent Application No. 58-93063. This method has the shortcoming that the undercoat layer decreases the chargeability of the photoconductor.